[jira] [Created] (NIFI-2713) Database Fetch processors' max-value columns don't work as expected

["Matt Burgess (JIRA)" <ji...@apache.org>]

Matt Burgess created NIFI-2713:
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             Summary: Database Fetch processors' max-value columns don't work as expected
                 Key: NIFI-2713
                 URL: https://issues.apache.org/jira/browse/NIFI-2713
             Project: Apache NiFi
          Issue Type: Bug
            Reporter: Matt Burgess
            Assignee: Matt Burgess


Currently, for QueryDatabaseTable and GenerateTableFetch, the user can enter any number of maximum-value columns, which are used to generate a SQL query that will fetch all records whose values are greater than the last-observed maximum values for those columns.

However this makes multiple max-value columns not very useful, since they will both have to increase in lockstep or records will be lost/skipped. In such a case, using one or the other (but not both) would suffice, making multiple max-value columns useless.

The more likely use case is that there are multiple columns whose values are strictly increasing, but at different rates. This is common with very large tables where a column could be for "date_created" and also a "bucket number" that strictly increases once a day. Queries for a day's worth of data are more efficient if they can be filtered on "bucket" (in this case), then on timestamp. However the generated SQL queries would have to reflect that "bucket" may remain the same as timestamp is increasing, but once the bucket value has increased, then only the (new) timestamps for that bucket should be fetched.



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